Dewaxing is a commonly used technique for improving the properties of a petroleum fraction for use in various products, such as lubricant base stocks. Typical dewaxing process feedstocks are raffinates from solvent extraction processes, wax vacuum gas stocks, hydrocrackates, and other wax-containing petroleum streams. Historically, solvent dewaxing was the first type of dewaxing used in the manufacture of lubricant base stocks. Solvent dewaxing, following a solvent extraction step, allowed for separation of a feedstock into a dewaxed base stock, an aromatics fraction, and a waxy fraction. More recently, catalytic dewaxing has been commonly used for improving the properties of feeds for use in lubricant base stocks.
Catalytic processing is commonly used for production of Group II and Group III type lubricant base stocks. During the various hydroprocessing and catalytic dewaxing steps involved in catalytic base stock production, a feedstock is usually exposed to multiple catalysts with at least some activity for saturating aromatic compounds. As a result, the catalytic processing steps used for improving the viscosity and other lubricant properties of Group II and/or Group III base stocks can also lead to reduction of the amount of aromatic compounds in the base stock.
U.S. Pat. No. 8,658,018 describes a lubricant base stock blend having a low wt % Noack volatility. The blends of lubricant base stocks include blends of light neutral base stocks having low aromatics content with Group I or Group II petroleum-derived base stocks. The blends are described as including at least 5 wt % of the Group I or Group II petroleum-derived base stock.